1. Field of the Invention
The present invention relates to an ultrasonic detector apparatus useful for non-destructive testing of mechanical equipment whereby ultrasonic frequency signals generated internally by the equipment may be detected and analyzed to identify impending mechanical failures.
2. Description of the Prior Art
Contemporary practice for maintenance and repair is primarily dependent upon the detection of audible sounds emitted from the equipment. Such audible sounds indicate a failure mode of operation, and do not generally occur substantially prior to failure to affect their timely repair. Current maintenance procedures generally include elaborate instrumentation, sensor installation, involved data collection and mathmodel analysis as well as the use of an expensive and highly trained engineering staff. Accordingly state-of-the art malfunction detectors normally involve physical attachment of at least a portion of the device to the mechanical equipment, and often utilize a signal reflected from the detector, rather than a signal generated by the equipment, as the means for analyzing and determining equipment malfunction.
U.S. Pat. No. 3,858,439 to Nakamura teaches such a method and apparatus wherein master sensors are actually placed on the structure to be tested. U.S. Pat. No. 3,986,391 to Vahaviolos teaches an apparatus for monitoring a continuous weld by detecting and processing stress wave signals emitted from the weld area as the material is heated and subsequently cooled. A similar teaching calling for physical contact of the sensor to the source of acoustic emissions is taught in U.S. Pat. No. 4,033,179. Finally U.S. Pat. No. 3,681,978 to Mathias shows a method and apparatus for automatically balancing a periodic deflection signal being produced by deflection sensors which are actually applied to a rotating body.
In contrast to these prior art devices, the present invention is non-destructive, passive in that the detector apparatus does not generate ultrasonic frequencies but merely receives, interrogates and stores them, and does not require attachment to or physical contact with the equipment being tested, thereby allowing substantial portability and ease of use. In principle the present invention teaches that the wearing of components within a piece of equipment emits signals in the ultrasonic frequency range which can be detected by a hand-held sensor while the equipment is still operating, also that these signals can be analyzed to detect an incipient malfunction, both normal and abnormal wear of the equipment, and, further, that such signals can be used to project time-to-failure of the equipment component. In view of the above, it is one object of the present invention to provide a means to detect an incipient malfunction which avoid the problems associated with the prior art and as yet unresolved.
Another object of this invention is to enable the detection of normal and abnormal wear without physical contact of the equipment while the equipment is still in its normal operation mode, and to enable analysis of the signals from the equipment with a minimum of technical expertise by use of a segmented display which indicates the result of a single test and by the use of plural displays to indicate the results of successive test series in order to discriminate between normal and abnormal wear. Yet another object of the present invention is to provide a decrease in ambient background noise to improve signal quality. Finally, it is further intended that use of the ultrasonic detector apparatus of this invention will enable the user to project a time-to-failure of the operational equipment, thereby establishing priorities of maintenance and economical equipment usage prior to its repair. Further objects of the invention will in part be obvious and will in part appear hereinafter.